A large number of mechanical looms for producing ribbons are known in the art. FIGS. 1 through 4 show four known basic methods of feeding a loop of weft thread 1, by means of a weft insertion needle 2, into a shed 4 created by warp threads 3. The loop of a weft thread 1 is inserted on one side of the shed 4, and on the opposite side of the shed 4 a knitting needle 5 is provided where one leg 6 of the weft thread loop 1 is inserted and tied. In FIGS. 1 through 4 all identical parts have the same reference numbers and the modified embodiments in FIGS. 1 through 4 are distinguished by the addition a through d.
In the embodiment variant in FIG. 1 the knitting needle 5a moves back and forth linearly, and the leg of weft thread 6a is inserted into the hook of the knitting needle by means of a press down device 7 that moves up and down. The press down device 7 represents an additionally activated component which complicates the design of a mechanical loom, increases the number of expendable parts, and in particular, it also has a negative effect on its performance. The design example in FIG. 2 is not equipped with a press down device. Instead, the knitting needle 5b is required to describe a down and up looped movement 8 in order to take hold of the leg of weft thread 6b. Again, additional mechanisms are required in order to achieve the knitting needle's 5b looped movement 8 which results in the above described disadvantages.
In the embodiment variant in FIG. 3 the knitting needle 5c moves in a circular path in order to catch the leg of weft thread 6c of the weft insertion needle 2c. This, however, is feasible only if the knitting needle 5c, which is a latch type knitting needle having a latch 74, moves in a large circular path W and moves back jerkily and quickly. This type of design is highly susceptible to wear and tear and to vibrations and is entirely unsuitable for high operating speeds. Also, compound needles cannot be used in this type of operation due to the knitting needle's long stroke.
In the known embodiment according to FIG. 4 the feeding path of the weft insertion needle 2d lies above the head of the knitting needle 5d. A guide wire 9 projects into the moving path of the weft insertion needle 2d and presses the leg of weft thread 6d to be tied downward into the hook running path of the knitting needle 5d. The guide wire 9 forms a diagonal guide track 10 running from top to bottom whose angle a must be small as otherwise the thread does not slide downward. For this reason, this systems requires a relatively large distance D, which, in turn, can be achieved only by increasing the length of stroke of the knitting needle 5d. The relatively long stroke limits the operating speed of the mechanical loom and makes it unsuitable for the use of compound needles. An additional disadvantage of this system is that the guide wire 9 also presses the other leg 11 of the weft thread loop 1d against the running path of the knitting needle 5d. This often has the result that the hook of the knitting needle 5d also takes hold of the second leg of weft thread 11. Typically, this causes the loop of weft thread to break and consequently the mechanical loom comes to a stop. In addition, in this system the eye of the weft insertion needle 2d that leads the weft thread must move far beyond the fell of the cloth and consequently beyond the guide wire. This requires a significantly longer weft insertion needle. As a result, the needle is heavier and thus more susceptible to vibrations. The mechanical loom is unsuitable for high operating speeds.
Finally, a mechanical loom of the type described in the introduction is known from GB-PS 552 067. However, here the guide plate is arranged between the knitting needle and the fell of the cloth in order to support the knitting needle and to prevent its deflection against the web of endless fabric. This arrangement makes it more difficult to tie off the knitted selvedge loop and to pull it in tightly and fit it closely against the web of endless fabric.
Typically, mechanical looms of the above described type are not suitable for operation with compound needles or latch type needles with short knitting needle strokes and allow operating speeds of no more than up to 2000 revolutions per minute.